Motorcycle with support wheel system

ABSTRACT

A vehicle ( 1 ) in the form of a motorcycle comprises a support wheel system located between the front and rear wheels ( 3, 4 ) of the motorcycle. The front wheel is arranged in a wheel suspension ( 5 ), in or with which the front wheel can, depending on steering actions with steering means ( 7 ), be turned into different desired turning steering positions. In the longitudinal section plane of the vehicle in the vertical direction, there is a projection (a) at the front wheel on account of the said suspension. The support wheel system is arranged to assign to the support wheels ( 10, 11 ) turning steering positions which depend on the turning steering positions of the front wheel and result in the vehicle, when performing turning steering in primarily the lower speed range of the vehicle, taking up with its said longitudinal section plane a vertical position or a position in relation to the said vertical position which is inclined slightly in the same direction (R) as the assigned turning steering direction of the front wheel. In this way, the driving standard can be raised considerably, especially at lower speeds.

The present invention relates to an arrangement for a vehicle in theform of a motorcycle with a support wheel system which is locatedbetween the front and rear wheels of the motorcycle. The front wheel isarranged in a wheel suspension, in or with which it can, depending onsteering actions with steering means (handlebars, steering wheel, leveretc.), be turned into different desired turning steering positions. Thevehicle is also of such a nature that, in its longitudinal section planein the vertical direction, there is what is known as a projection at thefront wheel on account of the said suspension.

The present invention constitutes a development of the inventionaccording to Swedish patent application 0001210-4 with filing date Apr.04, 2000 and the same applicant and inventor as the present application.

With regard to the state of the art, reference is made to the saidpatent application and the patent specification U.S. Pat. No. 4,203,500cited therein.

Like the said Swedish patent application, the presentinvention/development is based on the fact that a motorcycle feel is tobe present in the vehicle especially at high speeds. Unlike the saidAmerican patent specification, the present invention is also based onthe knowledge that the support wheels are to be in contact with theground throughout driving.

The said Swedish patent application also proposes that a scrubbingfunction (lateral displacement movements) is to be present within thelower speed range or crawling speed range.

There have proved to be problems at great front wheel deflections at lowspeeds, for example speeds of less than 5 km/h. Owing to the projectionreferred to in the introduction and the relatively high positioning ofthe centre of gravity, moments (which can be relatively great) arisewhich tend to incline the vehicle in a direction opposite to the turningdirection. This has to be compensated by the rider, for example byinserting a foot. The Swedish patent application mentions thatcompensation can also be effected by operable active means (for examplehydraulics).

It has nevertheless been found that the proposed scrubbing functionleads to twitches in the lateral inclination function of the vehicle andthat there are difficulties in effecting the said compensation byinserting a foot and/or the said operation of the active means.

A requirement therefore exists in the said driving situations with lowspeed and great steering deflection (the vehicle may have a turningdiameter of 5-6 metres) to raise the driving standard so that turning orchanging direction feels natural without risk of the vehicle overturningand without the said countermeasures having to be taken by the rider.

The present invention aims to solve inter alia this problem and theinvention can be considered to be characterized mainly in that interalia the support wheel system is arranged to assign to the supportwheels turning steering positions which depend on the turning steeringpositions of the front wheel and result in the vehicle, when performingturning steering in primarily the lower speed range of the vehicle,taking up with its said longitudinal section plane a vertical positionor a position in relation to the said vertical position which isinclined slightly in the same direction as the assigned turning steeringdirection of the front wheel.

In a preferred embodiment, the cross axis or cross axes of the supportwheels is or are arranged so that it or they is or are directed at leastessentially towards the centre of turning of the vehicle. The supportwheels are preferably arranged on a unit which bears the support wheelsand can be mounted on the vehicle chassis via a ball-and-socket joint bymeans of which at least three degrees of freedom are brought about withregard to the movement function of the support wheels. Steering dampingcan be arranged for the support wheel function, for example by means oftwo steering dampers, the geometry of which, in the ball-and-socketjoint embodiment, is arranged so that, when crawling, they limit thesteering angles of the support wheel axles and, when the vehicle is putinto a curve at high speeds, for example speeds above roughly 50 km/h,they provide a drift angle of, for example, 2-3° on the cross axis.Moreover, the system can have inclination and shock dampers, for exampleof conventional type.

In an alternative embodiment, the unit bearing the support wheels isarranged rotatably around or with an axis extending horizontally in thelongitudinal section plane. The unit bears steering joints for thesupport wheels, and the steering joints compensate for both lateralmovement and steering angle, which can take place positively or activelyby means of, for example, hydraulics or passively when use can be madeof steering dampers and possible locking functions for higher speeds.

In another embodiment, use is made of a central joint which compensatesfor the lateral movement and the steering angle of the cross axis. Inthis case as well, use can be made of active or passive steering(compare above).

In a further embodiment, the support wheel system comprises a unit whichbears the support wheels and is arranged rotatably in relation to thechassis of the vehicle in or around three main directions. In thisconnection, a first direction extends in the horizontal direction or ina slightly inclined manner in relation to the horizontal direction inthe said longitudinal direction plane of the vehicle. A second directionextends in the vertical direction in the said longitudinal directionplane, and a third direction extends at right angles to the saidlongitudinal direction plane. Further characteristics may be that afirst axis, for example the pivot axis or an inclination axis, around orwith which the unit is rotatable in a first direction of rotation,extends in the first direction, a second axis or a steering axis, aroundor with which the unit is rotatable in a second direction of rotation,extends in the second direction, and a third axis or spring-action axis,around or with which the unit is rotatable in a third direction ofrotation, extends in the third direction.

In one embodiment, use is made of inclination and shock dampers whichcan be regulated by or via an automatic balancing system. Alternatively,dampers can be coupled to hydraulic cylinders (hydraulics) and regulatedmanually (by the rider), for example via foot pedal(s).

Further developments of the inventive idea emerge from the followingsubclaims.

By virtue of the steerability of the support wheels achieved in thisway, the need for a scrubbing function and operation of active means incertain low-speed phases is eliminated. By virtue of the steerabilityand the combination of this with inclination in the right direction,lateral forces which otherwise force the vehicle to be inclined in thewrong direction can be eliminated. The vehicle can be steered with greatease even at the said low speeds and with great deflection of the frontwheel. A great freedom of choice can be obtained for the position of theside wheel system between the front and rear wheels.

Sometimes a position closer to the front wheel, which has been difficultto achieve in known systems, is desirable. A locking function at highvehicle speeds of the support wheels contributes to the possibility ofretaining the motorcycle feel in the higher speed range. By virtue ofthe active or passive steering of the support wheels, the support wheelsare in contact with the ground throughout driving of the vehicle. Thefeel of a car is obtained at low speeds.

A for the present proposed embodiment of an arrangement which has thefeatures significant of the invention will be described below withsimultaneous reference to accompanying drawings in which

FIG. 1 shows in perspective obliquely from above and from the rear adiagrammatically illustrated vehicle with a first embodiment of asupport wheel system;

FIG. 1 a shows on enlarged scale in relation to FIG. 1 a ball-and-socketmounting forming part of the system;

FIG. 2 shows diagrammatically in a horizontal view a second embodimentof the support wheel system;

FIGS. 3-3 d show various views of parts of a vehicle which uses a thirdembodiment of the support wheel system;

FIG. 4 shows in perspective from above and obliquely from the rear afourth support wheel system, which has the fundamental constructionaccording to FIGS. 3-3 d;

FIG. 5 shows in a horizontal view from above parts of the systemaccording to FIG. 4, and

FIG. 6 shows in side view examples of projection in the front wheelgeometry at different steering angles.

In FIG. 1, a vehicle is shown generally by 1. Only the parts to whichthe invention refers are shown. The chassis of the vehicle is indicatedby 2, a front wheel by 3, and a rear wheel by 4. The front wheel isarranged with a wheel suspension 5 comprising a fork 6 and handlebars 7.Engine, seat etc. are not shown for the sake of clarity. In the presentcase, the vehicle consists of a motorcycle which is provided with asupport wheel system 8 which, in the illustrative embodiment, comprisesa bow-shaped unit 9 which, at its outer or lower ends 9 a and 9 b, bearssupport wheels 10 and 11 which can be two or more in number. The unit 9is mounted on the chassis 2 via a ball-and-socket joint 12′ in itscentral parts. The unit 9 works with at least three degrees of freedomand is therefore arranged rotatably around or with three mutuallyperpendicular axes (compare conventional x, y and z axes) making itpossible for the support wheels to be turned depending on the turningmovements of the front wheel (the vehicle). Alternatively, one axis (thex axis) can be slightly inclined, for example backwards/downwards. Theturning movements of the support wheels take place counter to the actionof steering dampers 12 and 13 which, when the support wheels turn,strive to return the support wheels to the starting position whereturning is zero. The steering dampers are fixed to the chassis and theunit via their ends 12 a, 12 b and 13 a, 13 b. The support wheels aremounted on or provided with wheel axles 10 a, 11 a. Moreover, thevehicle 1 is provided with inclination and shock dampers 14 and 15 whichare fixed to the chassis and the respective support wheel at their ends14 a, 14 b and 15 a, 15 b. The said dampers 12, 13 and 14, 15 can be ofa kind known per se, for example those sold on the open market by ÖhlinsRacing AB under the designation SD121 (for 12, 13), or the shockabsorber principle applied in vehicle suspension in the basic type46PRCL (for 14, 15).

FIG. 1 a shows an illustrative embodiment of the construction of theball-and-socket joint. The ball-and-socket joint can consist of aball-and-socket joint known per se which is used within the vehiclesector.

The ball-and-socket joint has a first part 12 a′, by means of which itcan be anchored to the unit 9 (compare FIG. 1), for example by means ofa nut. The ball-and-socket joint also has a second part 12 b′, by meansof which it can be anchored to the chassis 2 (compare FIG. 1) which isindicated only symbolically in FIG. 1 a. In this connection, the part 12b′ can have an external thread 12 c′ which can interact with acorresponding internal thread in the chassis. The part 12 a′ is providedwith a spherical part 12 d′ at one of its ends. The spherical part 12 d′is mounted in a plastic body 12 e′ which is arranged at the end of thesecond part 12 b′ and comprises on the inside material/mass made ofrubber/plastic 12 f′. The ball-and-socket joint is arranged to allowrotations around three axes in a manner known per se. Compare alsoabove.

In the embodiment according to FIG. 2, the ball-and-socket joint hasbeen replaced by two steering axes (one for each support wheel) 16, 17,a spring-action axis 18 and an inclination axis (pivot axis) not shownspecifically in FIG. 2. The side wheels can be turned by means oflinkages (not shown specifically but see the description for FIG. 3below). Solid lines for the front and rear wheels 3′, 4′ and the sidewheels 10′ and 11′ indicate the positions when the vehicle standsvertically with its longitudinal section plane at right angles to thefigure plane of FIG. 2. Broken lines indicate the positions of the saidwheels and steering axes when the front wheel has been turned. In thisconnection, it is characteristic of the system that the vehicle isassigned a small inclination in the same direction as the direction ofturning R.

Alternatively, the inclination can be zero relative to the longitudinaldirection plane. In this case, the turning of the support wheels isactive and is determined by means of hydraulics 19 comprising ahydraulic cylinder. In an alternative embodiment, the adjustability isarranged passively in a known manner. By means of the hydraulics, ahydraulic cylinder 20 acting on the direction of turning of the supportwheel 10′ is operated. The support wheel 10′ in turn acts on the supportwheel 11′ via a track rod 21 so that the deflection of the two supportwheels 10′ and 11′ is essentially the same and dependent on the steeringdeflection of the front wheel, compare the angle α at the front wheeland the range β at the unit 9′. When turning takes place, the cross axes22, 23, 24 and 25 of the front and rear wheels and the support wheelsextend essentially through the centre of turning 26 of the vehicle.

In the illustrative embodiment according to FIG. 3, the individualsteering axes of the support wheels according to FIG. 2 have inprinciple been replaced by a common steering axis 27 for the unit 9″which is therefore arranged rotatably in the figure plane of FIG. 3. Thesupport wheels are not arranged steerably on the unit 9″ as in the caseaccording to FIG. 2. In this case as well, a spring-action axis 18′ ispresent. The support wheels 10″ and 11″ have a common cross axis 28which extends through the centre of turning of the vehicle as do thecross axes 22′ and 23′ of the front and rear wheels 3″ and 4″. Solidlines indicate the positions of the various components with the vehiclein vertical or upright position and the turning steering deflectionzero. Where the term longitudinal direction plane is referred to in thisapplication, this means the case when the vehicle takes up the saidvertical position in a plane at right angles to the figure plane of FIG.3. Broken lines indicate the case when the front wheel has been turned.In this case as well, the vehicle is slightly inclined in the directionof turning of the vehicle. In this case as well, it is conceivable toarrange the system in such a way that the vehicle takes up anon-inclined position when the said turning takes place. The unit 9″ ispositively controlled by hydraulics 19′ and a hydraulic cylinder 29(compare the case of FIG. 2). The unit 9″ can alternatively be passivelyadjustable in a manner known per se.

According to FIG. 3 a, the system includes an inclined axis 30 or pivotaxis around or with which the unit can be acted on so that, like theother embodiments described here, the support wheels 10″ and 11″ are incontact with the ground throughout driving of the vehicle. The unit 9″bears the support wheels 10″, 11″ on bearing axles 10 a′, 11 a′.

FIG. 3 b shows that the longitudinal axis 31 of the mounting of thefront wheel 3″ in the chassis is inclined, so that there is a projectiona.

FIG. 3 c shows the inclination of the axis 30 in the longitudinaldirection plane. The support wheels are mounted on their respectivebearing axles 10 a″ and 11 a″ (FIG. 3 a) via linkages 32.

FIG. 3 d shows the position of the rear wheel 4″ in the longitudinaldirection plane of the vehicle.

In accordance with FIG. 4, a backwardly/downwardly inclined firstaxis/pivot axis 30′ extends in a first direction in the longitudinaldirection plane of the vehicle. A steering axis/second axis 27′ extendsvertically in a second direction in the vertical plane of the vehicle. Athird axis/spring-action axis 18′ extends in a third direction at rightangles to the said longitudinal direction plane and the said second axis27′. In this case, the unit 9′″ is bow-shaped in its horizontal planeand is mounted with or on the steering axis 27′ in a part 33 formingpart of or associated with the chassis of the vehicle. The bearing axlesof the support wheels 10′″ and 11′″ are indicated by 10 a″ and 11 a″. Inthis case as well, use is made of a steering damper 13′ and inclinationand shock dampers 14′ and 15′.

In FIG. 5, the linkage at the support wheels 10′″ and 11′″ is indicatedby 32 a and, respectively, 32 b. The figure also shows the arrangementof the steering damper 13′ and its mounting on the chassis/the part 33via ends 13 a′ and 13 b′. The steering pin 27′ is mounted in the part33.

FIG. 6 shows the position of the front wheel in the longitudinaldirection plane or vertical plane. The front wheel suspension can havedifferent inclination directions 31′, 31″ and 31′″, the inclinationangles being indicated by α′, α″ and α′″. The ground plane is indicatedby 34, and a vertical axis through the centre of the wheel by 35. Theprojection is shown by α′. FIG. 6 is intended to show different steeringangles α′, α″ and α′″ with the same projection.

By virtue of the positive or passive deflection or turning of thesupport wheels depending on the steering of the front wheel, thecharacteristic and decisive function of inward inclination orinclination in the same direction as the steering direction R of thevehicle or the front wheel is obtained. Within their working range, thesteering dampers work with a damping function. In a fully extended orinserted position, an end stop function is performed, which defines amaximum deflection position for the support wheels.

The vehicle can be equipped with an automatic balancing system ormanually operable hydraulic cylinders which is or are arranged toregulate the inclination dampers and/or the shock dampers, for examplevia or with a foot pedal. Regulation can be effected in a manner knownper se and reference is made in this connection to FIG. 14 in theSwedish patent application referred to in the introduction.

It is important that the common steering axis 27 (FIG. 3) is able to bedisplaced a distance/range/gap β (see also FIG. 2) in the steeringdirection of the front wheel. Corresponding displacement takes placealso in the other embodiment of FIGS. 1 and 2 (see 12′, 18 and 30). Saiddisplacements effect the compensations for the lateral movements and thesteering angle deflections of the support wheels when the turningsteering movements of the vehicle take place. The compensation preventsthat the vehicle will be inclined in the wrong or outward direction inrelation to the steering direction of the vehicle. Such outwardinclination is abnormal at two wheels vehicles. The subject matter alsoallows driving conditions, in which the support wheels are in contactwith the ground even at high speeds, which increases the safety incurves at said high speeds.

The invention is not limited to the illustrative embodiments above butcan undergo modifications according to the following patent claims andthe inventive idea.

1. Arrangement for a vehicle in the form of a motorcycle with a support wheel system (8) located between the front and rear wheels (3, 4) of the motorcycle, and where the front wheel is arranged in a wheel suspension (5), in or with which the front wheel can, depending on steering actions with steering means (handlebars, steering wheel, lever, etc.) (7), be turned into different desired turning steering positions, and also where, in the longitudinal section plane of the vehicle in the vertical direction, there is a projection (a) at the front wheel on account of the said suspension, characterized in that the support wheel system is arranged to assign to the support wheels (10, 11) turning steering positions which depend on the turning steering positions of the front wheel and result in the vehicle, when performing turning steering in primarily the lower speed range of the vehicle, taking up with its said longitudinal section plane a vertical position or a position in relation to the said vertical position which is inclined slightly in the same direction (R) as the assigned turning steering direction of the front wheel, in that an imaginary axis or imaginary axes extending through the centres of the support wheels, here called cross axis (28) or cross axes (24, 25), extend essentially through the centre of turning (26, 26′) of the vehicle when turning of the vehicle takes place, and in that compensation for the lateral movements and the steering angle deflections of the support wheels at the turning steering movements of the vehicle are effected in accordance with one of the following options; a) in that the unit bearing the support wheels is mounted on the chassis via a ball-and-socket joint (12′) arranged to effect the compensation; b) in that the steering joints (16, 17) for the support wheels are arranged to effect the compensation by means of an active or passive arrangement, or c) in that, by means of its mounting with or around the vertical axis, a unit (9″) bearing of the support wheels (10″ 11″) effects the compensation either actively or passively by possible locking at higher speeds.
 2. Arrangement according to Patent claim 1, characterized in that it comprises a unit (9) which bears the support wheels and is mounted on the chassis (2) of the vehicle.
 3. Arrangement according to Patent claim 1, characterized in that the ball-and-socket joint (12) is arranged to allow movements of the unit around an imaginary axis extending in the longitudinal section plane and movements around another two imaginary axes which extend at 90° in relation to the imaginary axis extending in the longitudinal section plane.
 4. Arrangement according to Patent claim 1, characterized in that the unit bearing the support wheels is arranged rotatably around or with an axis extending essentially horizontally in the longitudinal section plane and bears steering joints for the support wheels, around or with which steering joints (16, 17) the support wheels (10′, 11′) are arranged rotatably relative to the unit (9′) bearing the support wheels in order to adjust themselves in their turning directions when turning of the vehicle takes place.
 5. Arrangement according to Patent claim 1, characterized in that the passive system includes or utilizes a locking function arranged so as to be activatable at higher speeds.
 6. Arrangement according to Patent claim 1, characterized in that the active system includes a steering function with a hydraulic cylinder (20) for one support wheel (10′) and a steering function by means of a track rod (21) from the said support wheel (10′) to the other support wheel (11′).
 7. Arrangement according to Patent claim 1, characterized in that the unit bearing the support wheels is arranged rotatably around or with an axis extending essentially vertically in the longitudinal section plane.
 8. Arrangement according to Patent claim 1, characterized in that the support wheels (10″, 11″) are mounted on the unit (9″) bearing the support wheels with or on bearing axis coinciding with a common cross axis (28) of the support wheels.
 9. Arrangement according to Patent claim 1, characterized in that the support wheel system comprises a unit which bears the support wheels and is arranged rotatably in relation to the chassis of the vehicle in or around three main directions (18′, 27′, 30′), a first direction extending in the horizontal direction or in a slightly inclined manner in relation to the horizontal direction in the said longitudinal direction plane of the vehicle, a second direction extending in the vertical direction in the said longitudinal direction plane, and a third direction extending at right angles to the said longitudinal direction plane.
 10. Arrangement according to Patent claim 9, characterized in that a first axis (30′), here designated an inclination axis, around or with which the unit is rotatable in a first direction of rotation, extends in the first direction, in that a second axis (27′), here designated a steering axis, around or with which the unit is rotatable in a second direction of rotation, extends in the second direction rotation, extends in the second direction, and in that a third axis (18′), here designated a spring-action axis, around or with which the unit is rotatable in a third direction of rotation, extends in the third direction.
 11. Arrangement according to Patent claim 1, characterized in that one or more steering damper(s) (12, 13) damping the deflection movement(s) is or are arranged between the chassis and the unit bearing the support wheels or assigned to elements associated with the support wheels, for example the bearing axles of the support wheels.
 12. Arrangement according to Patent claim 1, characterized in that the vehicle comprises inclination and shock dampers (14, 15) arranged between the chassis (2) and the unit bearing the support wheels.
 13. Arrangement according to Patent claim 12, characterized in that an automatic balancing system or manually operable, for example via a foot pedal, hydraulic cylinders is or are arranged to regulate the inclination and shock dampers.
 14. Arrangement according to Patent claim 1, characterized in that the steering dampers (12, 13) are arranged with an end stop function, in which the steering damping function changes into a stop function for the turning movements of the support wheels. 